Writing instrument



ug- 16, 1955 E. P. coFlELD, JR., ET AL 2,715,388

WRITING INSTRUMENT Filed April 29, 1955 INVENTORJ` EUGENE l? COF/ELU, J'l?. 5 By FRAN 655C Pwd y/ 6/Zw ATTORNEYS United States Patent O1 1 2,715,388 WRITING INSTRUMENT Eugene P. Colield, Jr., Atlanta, Ga., and Fran Seech,

Los Angeles, Calif., assignors to Scripta, Inc., a corporation of Georgia Application April 29, 1955, Serial No. 504,848 3 Claims. (Cl. 1Z0-42.4)

This invention relates to Writing instruments and more particularly to a fundamentally new type of writing instrument that combines certain desirable characteristics of lead pencils and of ball point pens.` It can perhaps best be identified as a pencil having an erasable, liquid lead, and a permanently sharp point.

A number of long desired but heretofore unobtainable features in writing instruments are provided for the iirst time in the writing instrument of this invention. For example, this instrument Writes like a wood case lead pencil, and the writing on paper therewith is erasable with the usual type of rubber eraser, yet the point of the instrument never requires sharpening and the ease and uniformity of writing on paper is comparable to that of ball point pens because the liquid lead used in this instrument ows from the writing point of the instrument with substantially the same ease and uniformity as the flow of ink from the ball of a ball point pen.

Another advantageous feature of the writing instrument of this invention is that the marks or writings produced on paper therewith, while having the color appearance of marks or writings produced with pencils and are similarly erasable, they are nevertheless smear and smudge-proof, as contrasted with the usual susceptibility of smudging encountered with pen ink writings.

Still another advantage of the writing instrument of this invention is that marks accidentally made on clothes, such as, for example, white shirts, with the writing point of this instrument are effectively removed by washing, as distinct from dicultly removable fountain pen ink stains.

The writing instrument of this invention, which possesses the foregoing and other novel features and advantages, comprises a suitable pencil barrel, a tube or other reservoir containing the liquid lead and having at one end a ball point to which the liquid lead is fed. The opposite end of the liquid lead tube may be closed with a plug having a tiny opening to provide atmospheric pressure within the tube. At the end of the barrel opposite the ball point, there may conveniently be provided a rubber eraser, just as in a wood case pencil, for erasing the writing or marks made on paper or other surfaces with the liquid lead.

The liquid lead used in the writing instrument of this invention has, as above suggested, certain properties similar to inks commonly used in ball point pens, and at the same time, properties similar to those possessed by the lead in a wood case pencil. However, this liquid lead has unique and novel properties not heretofore obtainable or used in any prior writing instrument, such as, for example, the property of writing like ink, yet being erasable with a common rubber eraser. This liquid lead does not contain the usual dyes or other indelible components commonly used in ink and which render the marks thereof indelible or non-erasable.

Also, this liquid lead distinguishes from the lead commonly used in a wood case or mechanical pencil, which is solid at ordinary temperatures and consists principally of graphite, clay and wax. The liquid lead of the present invention does not require any clay or wax and comprises a dispersion of very finely divided carbon such as carbon black or graphite, and a coacting liquid vehicle, with which the carbon forms a ne dispersion. This vehicle functions during the writing operation to cause limited penetration of the paper or other writing surice faces by the liquid vehicle and to eiect a deposit of the carbon principally on the surface of the paper such that it can be removed therefrom with an eraser.

The fine dispersion of the carbon particles in the somewhat viscous vehicle forms the liquid lead used in the Writing instrument of this invention, with or without the use of any other constituents. The unique writing properties and novel characteristics of this liquid lead involve a judicious selection of the constituents and a carefully controlled procedure for their compounding.

The liquid lead used in the writing instrument of this invention may contain graphite or carbon black of a suitable type, such as lamp black, furnace black, channel black, or thermal black. In the usual case, we have f found lamp black to be advantageous from the standpoint of particle size and uniformity of dispersion in the liquid vehicle. The vehicle used for producing the liquid lead dispersion is more viscous than Water, and has a consistency similar to syrup. It is physically of the nature of bodied mineral oil, resinous varnishes, and polymerized hydrocarbons. A vehicle that we have found to work very satisfactorily is a polyester resin manufactured by the Specialty Resins Company, Lynwood, California, and sold under the trade name Polyester Resin L-796. Another vehicle somewhat similar in physical characteristics, which we have used with good results, is a mineral oil ester gum varnish.

The proportions of the carbon and vehicle will vary somewhat with the diiferent speciiic forms of each, but generally will be of the order of 'l to i4 parts of the carbon to 100 parts of the vehicle. The minimum amount will depend upon the desired blackness or darkness of the writing. Also, the proportion of the carbon to the vehicle will vary with and depend upon the type of carbon used. The following are illustrative examples of the proportions of different carbon materials based, in each case, upon the use of 100 parts of vehicle:

Parts Lamp black 7 t0 14 Furnace black 7 to l0 Thermal black 7 to l0 Channel black 2 to 5 Graphite 5 to 14 Similarly, the size of the individual carbon particles (unflocculated) will Vary with the dijferent carbon materials, as follows:

Microns Lamp black 0.01 t0 0.4 Furnace black 0.045 to 0.075 Thermal black 0.045 to 0.075 Channel black 0.010 to 0.035 Graphite 3 or less exist between the ball and socket without blocking these passages;

(d) Form a surface deposit on the paper which is highly resistant to smudging but can be erased;

(e) Possess certain occulated and deflocculated structure under static and dynamic conditions, respectively.

The above requirements are made possible by obtaining in the liquid lead composition, a highly uniform and 2,715,sss

thorough dispersion of the carbon particles in the vehicle such that substantially each particle of carbon has been wetted by the vehicle, and also obtaining a controlled occulation of these wetted particles. We have found that the structure assumed by the carbon particles in this liquid lead composition is of substantial importance. lf, for example, the flocculated carbon particles produce a structure that is too rigid, the liquid lead will not Aflow suiciently under the influence of gravity to maintain a supply of lead at'the ball point. On the other hand, if the liquid lead structure is too loose, the carbon particles will not remain in a dispersed state and will ultimately settle out. Similarly, if the carbon particles are not suciently attracted to one another, they will pass between the yball and socket while the writing instrument is at rest and bleeding will result. Further, if the movement of the carbon particles is not suiciently restricted, they will penetrate the paper to such an extent that erasure of the Writing will be ditlcult.

In the liquid lead compositionthat has been perfected for satisfactory use in the present invention, the carbon particles are in such a state of flocculation that they cannot pass between the ball and socket unless their occulated state is disturbed, as by the rotating ball. The rotating ball exerts a shear that breaks down the occulated structure just suiliciently for the carbon particles to pass through the small clearances between the ball and socket, and upon deposit of these particles on paper they tend t0 revert to their original occulation state and consequently do not penetrate the paper too deeply.

These iocculation characteristics of the carbon particles are considered a very important feature of our invention. If there were complete dispersion of the carbon particles without any occulation, the liquid lead would undesirably pass the ball point when the writing instrument was not in use, and when it was in use the carbon particles would notdeposit on the surface of the paper as desired but would penetrate the paper and not be easily erasable. This ilocculated structure must beamenable to a break-down or partial deflocculation sutiicient to pass the ball point as a result of the shearing action of the ball during use of the writing instrument, and yet must have the property of reverting to the flocculated form when the liquid lead is deposited on the Writing sur face during Writing with this instrument. In this respect, the ilocculated structure is similar to a reversible colloid, and the three stages of (a) initial occulation under static conditions, (b) break-down under dynamic conditions, e. g., during writing, and (c) reocculation on the writing surface, are all important properties and functions of this novel liquid lead.

In the normal use of the writing instrument of our invention, the entire liquid lead composition, containing the carbon and vehicle, is transferred to the paper or writing surface, and the surface of the ball point, which has been in contact with the paper, is swept entirely clean.

The following are illustrative but non-limiting examples of formulas and procedures for preparing the liquid lead composition of our invention:

EXAMPLE l Vehicle Add one part Ester Gum 8L (manufactured by Hercules Powder Company) to fourparts Unitec 507 Mineral Oil (manufactured by Union Oil Company, Los Angeles, California). Mix until the ester gum is thoroughly dispersed in the mineral oil, and then heat at 200-250 F.vuntil the ester gum is completely dissolved. Filter while hot to remove any remaining solid matter. The resulting vehicle will have a viscosity of approximately 5000 centipoises at 70 F. when determined on a Brookfield synchroelectric viscometer (No. 4 spindle at 60 R. P. M.). Y

Liquid lead y Add one part Lampblack Germantown (manufactured ,these conditions for a period of about one hour.

by Monsanto Chemical Company, Camden, N YJ.) to live parts of the vehicle described above. Mix until a smooth dispersion is obtained and heat at l70-l80 F. for lS-24 hours or suiciently to wet the carbon particles with the vehicle and facilitate dispersion thereof. Cool and pass three times through a three-roll steel mill. The viscous paste thus formed is mixed with an additional quantity of the vehicle so that the lamp black and vehicle components exist in the ratioof 100 parts of the vehicle 'to 9 parts of the lamp black.

The' vehicle and lamp black constituents lare mixed in the above proportions until a smooth dispersion is obtained and this dispersion heated at l70-l80 F. from one to two hours. lt is then cooled and passed twice through the three-.roll steel mill and the product thus produced is placed in a vacuum chamber and brought again to a temperature of l70-l80 F. while under a vacuum of 27 inches mercury and maintained under The vacuum is then broken and the liquid lead is ltered through a fairly coarse felt and bottled for future use in the writing instrument of this invention.

EXAMPLE 2 Liquid lead Y Parts Vehicle: Polyester Resin L-796, manufactured by Specialty Resins Co., Lynwood, Calif l0() a. Furnace black: Molacco Black, manufactnred by Binney & Smith Co., New Yor f N. Y 7-l0 or b. Lamp black 8-12 or l c. Channel black: Peerless Blackf manufactured by Binney & Smith Co., New York, N. Y 5

or d. Thermal black: Sterling FT, manufactured by Godfrey L. Cabot, Inc., Boston, Mass 9 EXAMPLE 3 Liquid lead Vehicle: Polyester resin-Paraplex G-50/G-25,

manufactured by Rohm & Haas Co., Philadelphia, Pa 100 Lamp black 9 EXAMPLE 4' Vehicle: Non-drying alkydresin Beckosol No. 24, manufactured by Reichhold Chemicals,

Inc., Detroit, Mich l0() Lamp black Y 9 EXAMPLE 5 Vehicle: Polymerized hydrocarbons Polybutene,

manufactured by Oronite Chemical Company,

San Francisco, Calif 100 Lamp black 9 EXAMPLE 6 Vehicle: Polyester resin-Flexol Plasticizer RZH, manufactured by Carbide & Carbon Chemical Co., New York, N. Y 10i) Lamp black 9 EXAMPLE 7 Y Vehicle: Polymerized hydrocarbon lndopol l-I-35, manufactured by Indoil Chemical Company, Chicago, Ill 100 Lamp black 9 To prepare the liquid lead compositionof the `present invention using the various constituents identified above in Examples 2-7 inclusive, the procedure is somewhat diierent from that described in Example l above because of the fact that the vehicles used in these subsequent Examples 2-7 are already bodied or viscous in nature and therefore do not require reacting with a resinous material as was necessary for the mineral oil used in Example 1. Starting with the viscous resinous vehicles identified in Examples 2-7 and using the various types of carbon black identiiied therein, the procedure comprises generally adding one part of the carbon black, e. g., lamp black, to a portion, but not all, of the vehicle. For instance, when using Polyester Resin L-796, the one part of lamp black could be first mixed with four parts of this viscous resinous liquid and the mixing continued until a smooth paste is obtained and the paste heated at about 170 to 180 F. until the carbon black is thoroughly wetted by the resinous liquid, following which the mixture is cooled and passed three times through a three-roll steel mill.

Next, the remainder of the viscous resinous vehicle is added to the product resulting from the roll mill operation. Suicient additional vehicle is added to that product so that the components exist in the inal liquid lead composition in the ratios specified in the above examples. As shown in Examples 2-7, the amounts of carbon black are varied from about 5 parts to 12 parts, depending upon the type of carbon black and the type of vehicle, assuming 100 parts of vehicle.

Following this addition of the remainder of the vehicle to the previously prepared rolled paste, the resulting mixture is mixed and heated for about one to two hours at approximately 170 to 180 F., following which it is passed twice through the steel roll mill. The resulting liquid lead is then placed in a vacuum chamber, brought to a temperature of about 170 to 180 F. While under a vacuum of about 27 inches mercury and maintained under these conditions for a period of about one hour. Then atmospheric pressure is restored to the system and the liquid lead product is filtered through a suitable filter and bottled for subsequent use.

When it is desired to use graphite as the carbon material, the following formula and procedure may be employed:

EXAMPLE 8 Materials 35 gm. dipropylene glycol.

40 ml. triethanolamine.

40 gm. Amberol 820 (Rhom and Haas Company, Philadelphia).

35 ml. tetrahydrof'urfuryl alcohol.

45 gm. dag Dispersion No. 154 (graphite in alcohol) (Acheson Colloids, Port Huron, Michigan).

Procedure Mix dipropylene glycol, triethanolamine, and tetrahydrofurfuryl alcohol. Add Amberol 820. Heat, using an electric hot plate, until all Amberol 820 is dissolved. Transfer to a water bath. Add dag dispersion in small portions with stirring. Continue to heat and stir until substantially all of the alcohol initially contained in the dag dispersion has been evaporated. Allow to cool and mill three times on a three-roll steel mill.

A Writing instrument for utilizing an erasable liquid lead such as described above, is illustrated in a nonlimiting form in the accompanying drawing, in which:

Fig. 1 is an elevational view of the Writing instrument; and,

Fig. 2 is a corresponding view partly in section.

Referring to these two gures of the drawing, the writing instrument as shown comprises a barrel 10, a rubber eraser 11, and a ball point 12. Contained within the barrel 10 is a reservoir tube 13, which holds a supply of the liquid lead 14. The reservoir tube 13 may be made of metal, resin, plastic or any other suitable material. Into one end of this reservoir tube is tted a ball point insert 15, which terminates in a ball point socket 16 containing a writing ball 17.

At the rear end of the barrel 10 a metal ferrule 18 is arranged as a cap on which a sleeve 20 is tted to receive the eraser 11 and bore cover 19 therefor, and in which a suitable plug 21 is disposed for abutment with the top end of the reservoir tube 13. The plug 21 has an aperture 22 extending therethrough to permit venting of the ink tube 13 to the atmosphere.

In the foregoing description, the selection of constituents for the liquid lead composition and the proportioning of these constituents to provide certain viscosities, contemplate the use of gravity feeds for the liquid lead; that is, feeding of the liquid lead from the ink reservoir to the ball point under the inuence of atmospheric pressure only. Feeding of the liquid lead or other materials under superatmospheric pressure is disclosed and claimed in application Serial No. 499,076, tiled April 4, 1955.

This application is a continuation-in-part of our application Serial No. 429,927, tiled May 14, 1954.

Various other modifications and changes may be made in the above-described writing instrument and materials therefor as indicated in the scope of the appended claims.

We claim:

l. A writing instrument comprising a barrel, a reservoir within the barrel, a supply of liquid lead within the reservoir and a ball point connected to the liquid lead supply and located in writing position at one end of the barel, said liquid lead comprising a dispersion of carbon particles in a viscous, resinous liquid vehicle and said dispersion being in ilocculated form so as not to pass said bal point when the writing instrument is not in use, and being subject to break-down by the action of the ball point during writing for feeding thereby.

2. A writing instrument as defined in claim l and in which the liquid lead is fed to the ball point by gravity.

3. A writing instrument comprising a barrel, a supply of liquid lead housed within said barrel, and a ball point supported in writing position at one end of said barrel for feeding said liquid lead supply during writing, said liquid lead supply comprising carbon dispersed in a viscous liquid vehicle and flocculated sutiiciently to prevent the dispersion from passing said ball point when not in use for writing, and said dispersed carbon becoming deocculated under the shearing action of the ball point as it rotates during Writing for feeding said liquid lead supply.

4. A writing instrument as dened in claim 3 and further characterized in that the carbon dispersed in said viscous liquid vehicle is carbon black having an unflocculated particle size within the range of approximately 0.01 to 0.4 microns.

5. A writing instrument as defined in claim 3 and further characterized in that said carbon is dispersed in said viscous liquid vehicle in the proportion of approximately 2 to 14 parts to 100 parts of vehicle.

6. A writing instrument as dened in claim 3 and further characterized in that said viscous liquid vehicle is resinous in character.

7. A writing instrument as defined in claim 3 and further characterized in that said viscous liquid vehicle is oleaginous in character.

8. A Writing instrument as delined in claim 3 in which the carbon is graphite.

References Cited in the le of this patent UNITED STATES PATENTS 979,843 Grantham Dec. 27, 1910 2,107,424 Platt Feb. 8, 1938 2,220,621 Ellis Nov. 5, 1940 2,350,846 Vogel et al. .Tune 6, 1944 2,474,865 Salas July 5, 1949 FOREIGN PATENTS 162,454 Austria Mar. 10, 1949 633,879 Great Britain Dec. 30, 1949 

